@eno Wow, you really are incompetent. I mentioned my PhD in response to your comment that “Bragging about how well you read is no indication of how well you can comprehend.” My degree is an indication of how well I comprehend, especially when we’re talking about studies like this. So of course it doesn’t absolve me of all errors or free from criticism, but it does indicate that I can comprehend studies like this well. As for your comprehension of the study, I doubt you’ve read it. It seems like you’ve only read the news article you linked and the abstract available for free.
And yes, the lack of a control group is extremely important if we want to know whether the phenomenon is caused by whites or merely non-blacks. You claim it has to do specifically with whites, but there is no evidence that this is true. That’s why the authors say that there is no evidence of this: because they didn’t design the study in a way that could warrant that claim. Luckily, the authors are much more careful than you.
The cause (or “specific reason” in your terms) also matters because even if it has to be something negative, it doesn’t have to be something negative about the non-black associates. It could just be a matter of disliking people who do not show solidarity under conditions of oppression. If so, then the negative feeling would be entirely about other blacks. Now, I’m not saying this is the explanation. But the study provides no evidence either way, so we can’t responsibly draw a conclusion.
I notice, though, that you are changing your claim. You originally said that the study proved blacks were more prejudiced than whites. Now you’re just saying it shows that blacks are sometimes prejudiced. But I already said that blacks can be prejudiced. I think everyone so far agrees on that. It’s not the issue we’re discussing, though, so “proving” that doesn’t matter at all. Everyone agrees that blacks can be prejudiced and sometimes are. Everyone believes that blacks can be prejudiced against whites and sometimes are. You claimed to be proving that blacks are more prejudiced than whites, but you haven’t given us any evidence for that. At best, you’ve shown that sometimes blacks are prejudiced and that it might be caused by prejudice against whites.